Wiring patterns formed by selective metal plating

ABSTRACT

Conductive sidewall spacer structures are formed using a method that patterns structures (mandrels) and activates the sidewalls of the structures. Metal ions are attached to the sidewalls of the structures and these metal ions are reduced to form seed material. The structures are then trimmed and the seed material is plated to form wiring on the sidewalls of the structures.

FIELD OF THE INVENTION

The invention generally relates to connective sidewall wiring formed ina method where metal ions are attached to sidewalls and are then reducedto form seed materials. The structures are then trimmed and the seedmaterials are plated to form wiring on the sidewalls.

DESCRIPTION OF THE RELATED ART

As integrated circuits are reduced in size, the wiring that connectsactive and passive devices must also be reduced in size. This makes theconventional wiring more expensive and more resistive. One methodologyfor forming smaller wiring involves forming conductive materials alongthe sidewalls of insulating mandrels. These structures are sometimesreferred to as conductive sidewall spacers. If the mandrel is formed tothe minimum attainable lithographic dimensions, the sidewall wiring thatis formed along the structures is actually smaller than what can bepatterned lithographically. For a detailed discussion of such sidewallspacers see U.S. Pat. Nos. 5,331,116; 5,593,920; and 6,127,257 which areincorporated herein by reference.

SUMMARY OF THE INVENTION

One embodiment herein comprises a method of forming conductive sidewallwiring. This method patterns structures (mandrels) and activates thesidewalls of the structures. Next, metal ions are attached to thesidewalls of the structures and these metal ions are reduced to form aseed material. The structures are then trimmed and the seed materialsare plated to form wiring on the sidewalls of the structures.

The process of activating the sidewalls of the structures comprisesapplying a NH₃ plasma, O₂ plasma, etc. or TEOS or amine vapor/solutionto the sidewalls of the structures. The process of attaching the metalions comprises applying an aqueous solution of a metal compound, such asmetal nitrate, etc. to the sidewalls of the structures. The process ofreducing the metal ions comprises applying a H₂ vapor or a hydrazinesolution to the metal ions. A cap can also be formed on the structuresprior to forming the seed materials. In addition, the trimming processtrims loops of the seed material that are formed around sidewalls of themandrels.

This produces a wiring structure that has seed material on the sidewallsof the structure, and plated metal wiring on the seed material andsidewalls of the structure. This plated metal wiring therefore comprisesmultiple metal layers that are non-symmetric along the vertical sidewallsurfaces. The sidewalls have one of amino and carboxylic acidfunctionalities after they are activated by the NH₃ plasma, O₂ plasma,or TEOS or amine vapor/solution. The mandrel structure can comprise anorganic polymer, such as a photoresist, etc.

These, and other, aspects and objects of the present invention will bebetter appreciated and understood when considered in conjunction withthe following description and the accompanying drawings. It should beunderstood, however, that the following description, while indicatingembodiments of the present invention and numerous specific detailsthereof, is given by way of illustration and not of limitation. Manychanges and modifications may be made within the scope of the presentinvention without departing from the spirit thereof, and the inventionincludes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following detaileddescription with reference to the drawings, in which:

FIG. 1 is a schematic cross-sectional diagram of a partially completedwiring structure;

FIG. 2 is a schematic cross-sectional diagram of a partially completedwiring structure;

FIG. 3 is a schematic cross-sectional diagram of a partially completedwiring structure;

FIG. 4 is a schematic top-view diagram of a partially completed wiringstructure;

FIG. 5 is a schematic top-view diagram of a partially completed wiringstructure;

FIGS. 6A and 6B are schematic top-view diagrams of a partially completedwiring structure;

FIG. 7 is a schematic top-view diagram of a partially completed wiringstructure;

FIG. 8 is a schematic cross-sectional diagram of a partially completedwiring structure;

FIG. 9 is a schematic cross-sectional diagram of a partially completedwiring structure according to one embodiment;

FIG. 10 is a schematic cross-sectional diagram of a partially completedwiring structure according to one embodiment;

FIG. 11 is a schematic cross-sectional diagram of a partially completedwiring structure according to another embodiment;

FIG. 12 is a schematic cross-sectional diagram of a partially completedwiring structure according to another embodiment;

FIG. 13 is a schematic cross-sectional diagram of a partially completedwiring structure according to another embodiment;

FIG. 14 is a schematic cross-sectional diagram of a partially completedwiring structure according to another embodiment;

FIG. 15 is a schematic cross-sectional diagram of a partially completedwiring structure according to yet another embodiment;

FIG. 16 is a schematic cross-sectional diagram of a partially completedwiring structure according to yet another embodiment;

FIG. 17 is a schematic cross-sectional diagram of a partially completedwiring structure according to yet another embodiment;

FIG. 18 is a schematic cross-sectional diagram of a partially completedwiring structure according to yet another embodiment;

FIG. 19 is a schematic cross-sectional diagram of a partially completedwiring structure according to yet another embodiment;

FIG. 20 is a schematic cross-sectional diagram of a partially completedwiring structure according to yet another embodiment;

FIG. 21 is a schematic cross-sectional diagram of a partially completedwiring structure according to and additional embodiment; and

FIG. 22 is a schematic cross-sectional diagram of a partially completedwiring structure according to an additional embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

As mentioned above, conductive sidewall spacers can be utilized asextremely dense wiring and conductive plates for capacitive structures.However, conventional methodologies for manufacturing conductivesidewall spacers have difficulty forming such structures withhigh-aspect ratios. Further, it is sometimes difficult to control wherethe sidewall spacers are actually formed, which can result in open orshort circuits. Therefore, the following methodology has been developedto produce a structure that has a very high aspect ratio and that easilydefines where the conductive sidewalls will be formed.

More specifically, as shown in cross-sectional representation in FIG. 1,this method begins by forming a mandrel material 12, such as any commoninsulator including oxides, glasses, polymers, organic materials, etc.on any form of substrate 10, such as a silicon or non-silicon wafer,etc. Next, as shown in cross-section view in FIG. 2, the inventionpatterns an optional cap 22, such as a silicon nitride or similarmaterial over the mandrel material 12. More specifically, the capmaterial 22 can be deposited across the entire mandrel material 12, andthen a separate photoresist mask 24 can be patterned over the capmaterial 22. The photoresist mask can then be exposed, developed, etc.,as is well-known in the art. Then, the cap material 22 can be patternedby reactive ion etching (RIE) using the photoresist mask 24. Then,directional RIE can be utilized to pattern the mandrel material 12 intoinsulating mandrels 20.

Next, the invention activates the sidewalls of the structures byapplying a NH₃ plasma, O₂ plasma, or TEOS (Tetraethyl Orthosilicate, Si(OC₂H₅)₄), or amine vapor/solution to the sidewalls of the structures,as shown by arrows 26 in FIG. 2. The process of activating the sidewallsconditions the mandrel material 20 so as to provide them with organicamino, carboxylic acid, hydroxyl, etc., functionalities. Therefore, inaddition to the activating plasmas, vapors, or solutions mentionedabove, any treatment that will provide organic amino, carboxylic acid,etc. functionalities to the sidewalls will be useful with the invention.

For example, deposition of maleic anhydride polymer by plasma CVDmethods can be followed by activation with a dendritic amine. Theactivation with the amine can be performed after the trim step ifdesired, in order to avoid interactions between the resist chemistry ofthe trim mask and the amine material. The plasma polymerized maleicanhydride is non-selective, and will deposit on all surfaces of thesubstrate. It can be etched with an oxygen RIE to remove the materialsfrom the horizontal surfaces, leaving a thin spacer of polymer materialon the sidewalls of the mandrel. The amine dendrimer can be applied as amethanol solution, (polyamidoamine, 10% w/v in methanol), followed by amethanol rinse. Alternatively, a soluble maleic anhydride polymer orcopolymer can be spin applied and soft-baked, and used directly as themandrel material, being activated with amine solution after etch anddevelop. Alternatively, a resist formulation containing a reactivecomponent such as maleic anhydride polymer or copolymer can beimage-wise exposed and developed, followed by activation with amine. Theamine material can be removed from the horizontal surfaces of the resistimage by means of oxygen or argon RIE, leaving the sidewalls of theresist functionalized with amine.

In another method, ammonia plasma can be used to aminate mandrelsurfaces. An Ar or oxygen RIE can be used to clean horizontal surfacesprior to metal deposition. Hydrogen Silsesquioxane materials can be usedto form the mandrel, and can be left in place in the semiconductordevice as part of the dielectric material, if desired. An organicMandrel could also be used in this method.

In another method, plasma polymerized acetaldehyde, acetic acid, ordiamino-ethane, or similar materials, can be deposited on the mandrelsurface. Ar or oxygen RIE can be used to remove these materials fromhorizontal surfaces, leaving a thin spacer of polymer material on thesidewalls of the mandrel. The aldehyde, carboxylic acid or aminefunctionalities remaining on the mandrel sidewall can be used to bindmetal ion seed layer materials to the sides of the mandrel.

In another method, the mandrel itself can be composed of a materialcontaining active amine or carboxylate species as part of the material,either as an additive to a polymer matrix or as a component of thepolymer itself.

The photoresist 24 can be removed at any point after the cap material 22is patterned, as shown in cross-section in FIG. 3. Next, as also shownin FIG. 3, metal ions, such as palladium, platinum, Ni, Rh, Ru, Co, Ag,Cu, Pt ions (can be used to reduce copper 11 ions to copper metal,etc.), are attached to the sidewalls of the structures 20, and thesemetal ions are reduced to form metallic seed materials 40. The processof attaching the metal ions comprises applying an aqueous solution ofmetal compounds, such as metal nitrate, chlorides, bromides, fluorides,sulfates, sulfonates, phosphates, tetrafluoroborates,hexafluorosulfates, acetylacetonates, or similar materials, etc., to thesidewalls of the structures. Organometallic reagents might also be used,either as a vapor or in solution, such as (methylcyclopentadienyl)trimethylPlatinum, or carbonyls such as nickel carbonyl ((Ni(CO)₄),which is a gas at ambient conditions.

The process of reducing the metal ions comprises applying a hydrogen orhydrogen diluted with Argon or other inert gas, e.g., He, Ne, N₂, attemperatures from ambient to 400 C, depending on the metal to bereduced. Hydrazine or alkyl hydrazines could also be used as a reducingagent in solution to the metal ions. FIG. 4 illustrates the samestructure shown in FIG. 3 from a top-view.

The mandrels 20 are then trimmed as shown in top-view in FIGS. 5-6B.More specifically, a mask 50 (such as a photoresist or hard mask) isformed, as shown in FIG. 5. Then, using the mask 50, the end of themandrels 20 (and the seed material 40) can be trimmed using anywell-known material removal process, such as wet or dry etching,chemical rinsing, etc. as shown in FIG. 6A. Alternatively, as shown inFIG. 6B, the mandrels 20 can be allowed to remain in place while thenon-protected areas of the seed material 40 are removed through aselective etching or chemical rinsing process. This process selectivelytrims the loops of the seed material 40 that were formed around thesidewalls of the mandrels 20 into individual length of seed materialthat will be used in a subsequent plating process to form individuallinear conductive sidewall plated structures.

More specifically, as shown in top-view in FIG. 7 and cross-sectionalview in FIG. 8, the seed materials are plated with a conductive material70 (such as copper, palladium, platinum, etc.) to form wiring on thesidewalls of the structures. This plating process can comprise anywell-known electrical or non-electrical based plating process and can beused with any type of metal that easily plate to the seed material 40.As would be understood by one ordinarily skilled in the art given thisdisclosure, the seed material 40 is selected to be compatible with thematerial 70 which is plated onto the seed material 40 and any types ofconductive materials that will easily plate together can be used withthe invention. Therefore, the invention is not limited to the materialsthat are discussed above, but instead the foregoing materials are merelyused as examples. The wiring comprises the remnants of the seed material40 and the plated material 70, both of which are conductive (platedconductor).

Then, as shown in FIG. 9, a selective material removal process such asetching, chemical rinsing, etc. is utilized to remove the cap 22 and themandrel 20, leaving the plated wiring 70 and the seed material 40remaining freestanding. Then, as shown in FIG. 10, the entire structureis covered by an insulator 100, such as silicon dioxide, fluorinatedsilicon dioxide, or other known low-K dielectric films, as well as TaN,TiN, Ta, WN, which can be planarized as shown in FIG. 10. This producesa final wiring structure that has a seed material 40 and plated wiring70 on the seed material 40 separated by insulator 100. This platedwiring therefore comprises multiple metal layers (40, 70) that arenon-symmetric vertically.

Another embodiment is shown in FIGS. 11-14 which begins with thestructure shown in FIG. 8, but use different processing stepsthereafter. More specifically, as shown in FIG. 11, an insulator 110,such as any of the insulators discussed above, is deposited over thestructure. The structure is planarized as shown in FIG. 12 which removesthe cap 22. Next, as shown in FIG. 13, the seed material 40 and theplated wiring 70 are removed using any well-known selective removalprocess to leave openings 130 between the insulating materials 20, 110.Next, as shown in FIG. 14, the openings 130 are lined with a dielectricliner 140 and then filled with any form of conductor 142 and a damasceneprocess.

Yet another embodiment is shown in FIGS. 15-21. This embodiment alsobegins with the structure shown in FIG. 8 and coats the structure withan additional cap material 150 which can be, for example, silicondioxide deposited using a plasma process. Next, as shown in FIG. 16, adielectric 160 such as a black diamond dielectric is deposited over thestructure and the structure is planarized to remove the cap 22. Then, asshown in FIG. 17, another dielectric 170 (similar to the dielectricsdiscussed above) is deposited over the structure and another layer ofcap material 172 is patterned over the structure in a similar manner asthe discussed above. Then, a material removal process is utilized toform openings 174 through the insulator 170 and a portion of the mandrel20.

Next, as shown in FIG. 18, the openings 174 are filled with any form ofconductor 180 and the structure is planarized. Next, as shown in FIG.19, openings 190 are patterned in the cap layer 172 using similarprocessing to that discussed above. As shown in FIG. 20, a materialremoval process is performed through the openings 190 to remove theinsulator 170 and the mandrels 20. This leaves air as an insulatorbetween the conductors formed by the seed material 40 and the platedmaterial 70.

As shown in FIG. 21, another embodiment can stack the structure shown inFIG. 20 by repeating the processing shown above. Note that in thisembodiment, each conductor 180 is insulated by the cap material 150 andinsulator 160 from the conductive seed material and plated material 40,70 of the overlying layer. This is accomplished by aligning the layersdifferently. Another embodiment can align the layers similarly to allowthe conductors 180 and each layer to be electrically connected by theconductive seed material and plated material 40, 70, as shown in FIG.22.

The present invention and the various features and advantageous detailsthereof are explained more fully with reference to the nonlimitingembodiments that are illustrated in the accompanying drawings anddetailed in the description, above. It should be noted that the featuresillustrated in the drawings are not necessarily drawn to scale.Descriptions of well-known components and processing techniques areomitted so as to not unnecessarily obscure the present invention. Theexamples used herein are intended merely to facilitate an understandingof ways in which the invention may be practiced and to further enablethose of skill in the art to practice the invention. Accordingly, theexamples should not be construed as limiting the scope of the invention.

The invention allows wiring patterns to be formed which are very narrowand of very high aspect ratio, and with small image width tolerancevalues across the chip, wafer, or batch of wafers. The pattern is formedby selective deposition, using a process that is surface limited andtherefore highly conformal. The width of such patterns are determined bythe deposition time and deposition conditions, rather than by maskuniformity, optics uniformity, focus control of a stepper, exposure doseuniformity, or etch uniformity across a wafer or across a chip. The highaspect ratio of the wiring features aids in reducing capacitance, as athicker dielectric layer may be used to separate adjacent wiring masklevels. Reduced capacitance enhances chip speed, or performance.

While the invention has been described in terms of embodiments, thoseskilled in the art will recognize that the invention can be practicedwith modification within the spirit and scope of the appended claims.

1. A wiring structure comprising: a structure having sidewalls; a seedmaterial on said sidewalls of said structure; and plated wiring on saidseed material and sidewalls of said structure.
 2. The wiring structureaccording to claim 1, wherein said sidewalls have one of amino,carboxylic acid, and hydroxyl functionalities.
 3. The wiring structureaccording to claim 1, wherein said seed material and said plated wiringform a non-symmetric vertical structure on said sidewalls of saidstructure.
 4. The wiring structure according to claim 1, wherein saidseed material comprises metal.
 5. The wiring structure according toclaim 1, wherein said plated wiring comprises trimmed wires.
 6. Thewiring structure according to claim 1, wherein said structure comprisesan organic polymer.
 7. The structure according to claim 1, wherein saidstructure having sidewalls comprises one of SiO₂, FSiO₂, TaN, TiN, Ta,WN.
 8. A wiring structure comprising: a structure having sidewalls; aseed material on said sidewalls of said structure; and plated wiring onsaid seed material and sidewalls of said structure, wherein said platedwiring comprises multiple metal layers.
 9. The wiring structureaccording to claim 8, wherein said sidewalls have one of amino,carboxylic acid, and hydroxyl functionalities.
 10. The wiring structureaccording to claim 8, wherein said seed material and said plated wiringform a non-symmetric vertical structure on said sidewalls of saidstructures.
 11. The wiring structure according to claim 8, wherein saidseed material comprises metal.
 12. The wiring structure according toclaim 8, wherein said plated wiring comprise trimmed wires.
 13. Thewiring structure according to claim 8, wherein said structure comprisesan organic polymer.
 14. The structure according to claim 8, wherein saidstructure having sidewalls comprises one of SiO₂, FSiO₂, TaN, TiN, Ta,WN.
 15. A method of forming wiring, said method comprising: patterningstructures; forming a seed material on sidewalls of said structures;trimming said structures; and plating metal on said seed material toform said wiring on said sidewalls of said structures.
 16. The methodaccording to claim 15, wherein said process of forming said seedmaterial comprises: activating said sidewalls of said structures;attaching metal ions to said sidewalls of said structures; and reducingsaid metal ions to form said seed material.
 17. The method according toclaim 16, wherein said process of attaching said metal ions comprisesapplying an aqueous solution of metal nitrate to said sidewalls of saidstructures.
 18. The method according to claim 16, further comprisingforming a cap on said structures prior to forming said seed materials.19. The method according to claim 16, wherein said structures comprisemandrels and said trimming process trims loops of said seed materialthat are formed around sidewalls of said mandrels.
 20. A method offorming wiring, said method comprising: patterning structures;activating said sidewalls of said structures; attaching metal ions tosaid sidewalls of said structures; reducing said metal ions to form seedmaterials; trimming said structures; and plating said seed materials toform said wiring on said sidewalls of said structures.
 21. The methodaccording to claim 22, wherein said process of attaching said metal ionscomprises applying an aqueous solution of metal nitrate to saidsidewalls of said structures.
 22. The method according to claim 22,further comprising forming a cap on said structures prior to formingsaid seed materials.
 23. The method according to claim 22, wherein saidstructures comprise mandrels and said trimming process trims loops ofsaid seed material that are formed around sidewalls of said mandrels.24. A method of forming wiring, said method comprising: forming mandrelson a substrate; plating sidewalls of said mandrels with a platedconductor; covering said mandrels and said plated conductor with aninsulator; removing said conductor to leave openings between saidmandrels and said insulator; and filling said openings with a damasceneconductor.
 25. The method in claim 24, wherein said plating processcomprises: forming a seed material on sidewalls of said mandrels;trimming said mandrels; and plating said seed material to form saidplated conductor on said sidewalls of said structures.
 26. The method inclaim 25, wherein said process of forming said seed material comprises:activating said sidewalls of said structures; attaching metal ions tosaid sidewalls of said structures; and reducing said metal ions to formsaid seed material.
 27. The method according to claim 26, wherein saidprocess of attaching said metal ions comprises applying an aqueoussolution of metal nitrate to said sidewalls of said structures.
 28. Themethod according to claim 25, wherein said trimming process trims loopsof said seed material that are formed around sidewalls of said mandrels.29. A method of forming wiring, said method comprising: forming mandrelson a substrate; plating sidewalls of said mandrels with a platedconductor; coating said mandrels and said plated conductor with a firstcap material; filling spaces between said mandrels with an insulator;planarizing said structure to expose said mandrels; forming asacrificial material above said mandrels and said insulator; patterninga second cap material over said sacrificial material; patterning saidsacrificial material through openings in said second cap material;depositing a conductor in openings in said sacrificial material; formingadditional openings in said second cap material; and removing saidsacrificial material and said mandrels through said additional openings.30. The method in claim 29, wherein said plating process comprises:forming a seed material on sidewalls of said mandrels; trimming saidmandrels; and plating metal on said seed material to form said platedconductor on said sidewalls of said structures.
 31. The method in claim30, wherein said process of forming said seed material comprises:activating said sidewalls of said structures; attaching metal ions tosaid sidewalls of said structures; and reducing said metal ions to formsaid seed material.
 32. The method according to claim 31, wherein saidprocess of attaching said metal ions comprises applying an aqueoussolution of metal nitrate to said sidewalls of said structures.
 33. Themethod according to claim 30, wherein said trimming process trims loopsof said seed material that are formed around sidewalls of said mandrels.